Many asymptomatic HIV-infected individuals develop alveolitis followed by emphysema but the pathogenesis remains unknown. We have found that cytotoxic lymphocytes (CTLs) are elevated in the airway of subjects that develop emphysema and that these patients have substantial morphologic evidence of parenchymal tissue loss. This corroborates other studies demonstrating that CTL elevation coincides with an early decline in diffusion capacity and an increase in lower airway epithelial permeability. A key observation is that CTLs isolated from the lung of HIV-infected subjects can accomplish MHC class 1 restricted killing of HIV infected cells. The focus of this investigation is to expand on a series of ground-breaking discoveries made by the applicant that reveal the following, 1) 141V infects human lung epithelial cells in vivo and in vitro; 2) the lung epithelium is permissive to HIV replication; and 3) that HIV infection of lung epithelial cells induces CTL-mediated apoptosis in an MHC restricted manner. Specific Aim 1 will test the hypothesis that primary human lung epithelial cells are infected by HIV-1 from the apical and basolateral surface and permit viral replication following cell (NF-0) activation. We predict that this will result in the release of competent free virus. Specific Aim 2 will test the hypothesis that HIV infection of primary human lung epithelial cells triggers a CTL-mediated assault resulting in epithelial cell apoptosis. In this pursuit we will identify the mechanism by which epithelial cell apoptosis occurs and then determine if a potent epithelial cell mitogen, keratinocyte growth factor, can prevent lung epithelial cell death. In the revised application we will develop a physiologically relevant model for studies with HIV. In particular, primary human lung epithelial cells will be grown on collagen coated trans-well inserts to establish fully differentiated monolayers with tight junctions at an air-liquid interface. The model will be used to identify preferential HIV transport which we believe is highly relevant since the epithelium may serve as a portal for HIV entry into the lung (basolateral to apical) as well as reintroduce virus back into the circulation (apical to basolateral). Subsequent studies will utilize the same model to identify how autologous, HIV-specific, CTLs dispose of the HIV+ lung epithelial cell. The long-term goal of the applicant is to establish a career in translational research that connects his current expertise in clinical medicine with basic science. The candidate has made a substantial commitment to pursue a career that will explore the lung parenchymal response to inflammation and translate discoveries into useful solutions for patients with lung disease. The applicant has established an excellent group of advisors to assist in this endeavor and has secured the appropriate institutional support to complete the training.